A lazy Friday afternoon, and you made the mistake of eating a big greasy burger with fries and washing it down with a couple o' brewskis. The thought of returning to the office was about as appetizing as coming down with food poisoning. Nobody in the shop would miss you anyway, you reasoned, at least not for a couple of hours. You entered the perpetually empty shopping oasis known as the downtown St. Paul Dayton's, escalatored your way to the fourth-floor furniture department. Took your time testing out the beds, then slipped off your shoes and... On a busy day there may be a shopper or two around, and perhaps a stray daydreaming salesclerk, but amid the acres of empty space up here, you could go undetected for days. But be forewarned: With the St. Paul Dayton's (er, make that Marshall Field's) set to undergo a $20 million face-lift, this sleepatorium's days might be numbered.